Ice-maker control circuit with slab limiting control

Claim 2

A slab thickness limiting control circuit for an automatic ice maker of the type having an inclined refrigerated plate cooled by a refrigerant circuit and with water circulated thereover by an electric motor driven pump to build up a finished slab of ice thereon and further including an inclined ice cutting grid to receive the ice slab from the refrigerated plate when released therefrom by hot gas defrost means and with the grid serving to cut the slab into individual cubes comprising; first and second mercury ice thickness control thermostatic control switches, a normally opened grid switch being closed when a slab of ice is receiver on the cutting grid from the freezing plate, a first transistor having a base, an emitter and a collector, a second transistor having a base, an emitter and a collector, a DC power source including first and second terminals thereon, means including first and second biasing resistors connected respectively to the base of said first transistor and the base of said second transistor, normally closed first switch means for connecting the base of said first transistor to said first mercury ice thickness control thermostatic control switch, means including second switch means having a normally closed contact for energizing the refrigerant circuit to cool the plate and a normally open contact operable to a closed position for defining an electrical path for conditioning the hot gas defrost means to defrost the refrigerated plate during a slab release cycle of operation, said first mercury ice thickness control thermostatic switch being positioned a first preselected distance above the refrigerated plate to detect a buildup of a first predetermined thickness of ice in the slab and operative to open to produce a bias on the base of said first transistor when the grid switch is normally open to cause said transistor to be forwardly biased, means including a coil connected in circuit relationship with the emitter and collector of said first transistor and operable when said first transistor is conductive to open said normally closed first switch means and to shift said second switch means from its normally closed contact to its normally open contact, said second ice thickness control thermostatic switch being positioned a preselected greater distance above the refrigerated plate than said first ice thickness control thermostatic switch to detect an excessive slab thickness, means including said second ice thickness control thermostatic switch for producing a negative bias on the base of said transistor to cause said second transistor to be triggered conductive, a third normally closed switch means in series with said first switch means and being maintained normally closed to complete the water pump motor circuit, means responsive to said second transistor being triggered conductive to open said third switch means to deenergize said water pump when an excessive ice buildup is detected by said second ice thickness control thermostatic switch.

Claim 3

A slaB limiting control circuit for association with a solid state refrigeration control circuit of the type including a first power transistor forwardly biased by means including an ice thickness sensor mercury thermostat to selectively position a solenoid operated relay to energize either a water circulating pump motor or a hot gas recirculation valve and wherein the base circuit of the transistor is connected to a switch that detects release of a slab of ice from an evaporator to direct a reverse bias signal to the transistor to cause the solenoid operated relay to be positioned in a water circulation mode when the slab of ice has been released from the evaporator plate the improvement comprising; circuit means including a second ice thickness sensor mercury thermostat switch for detecting an excessive buildup of ice slab thickness on the refrigerated plate, a second transistor having a base collector and emitter, circuit means including a biasing resistor in circuit relationship with said second ice thickness sensor mercury thermostat, normally closed switch means for completing the energization circuit for the water pump motor, circuit means connected across the collector emitter of said second transistor including means for operating said normally closed switch means to deenergize the water pump motor when said second transistor is turned on for current flow across its collector emitter electrodes, said second ice thickness sensor mercury thermostat being operative to trigger said second transistor to complete the conducting circuit between its collector and emitter to condition said normally closed switch means to terminate energization of said water pump motor thereby to prevent excessive build-up of ice slab thickness on the refrigerated plate when the slab switch is maintained closed during a refrigeration cycle of operation.

Claim 4

A slaB limiting control circuit for association with a solid state refrigeration control circuit of the type including a first power transistor forwardly biased by means including an ice thickness sensor mercury thermostat to selectively position a solenoid operated relay to energize either a water circulating pump motor or a hot gas recirculation valve and wherein the base circuit of the transistor is connected to a switch that detects release of a slab of ice from an evaporator to direct a reverse bias signal to the transistor to cause the solenoid operated relay to be positioned in a water circulation mode when the slab of ice has been released from the evaporator plate the improvement comprising; circuit means including a second ice thickness sensor mercury thermostat switch for detecting an excessive buildup of ice slab thickness on the refrigerated plate, a second transistor having a base collector and emitter, circuit means including a biasing resistor in circuit relationship with said second ice thickness sensor mercury thermostat, normally closed switch means for completing the energization circuit for the water pump motor, circuit means connected across the collector emitter of said second transistor including means for operating said normally closed switch means to deenergize the water pump motor when said second transistor is turned on for current flow across its collector emitter electrodes, said second ice thickness sensor mercury thermostat being operative to trigger said second transistor to complete the conducting circuit between its collector and emitter to condition said normally closed switch means to terminate energization of said water pump motor thereby to prevent excessive build-up of ice slab thickness on the refrigerated plate when the slab switch is maintained closed during a refrigeration cycle of operation.

Claim 5

A control circuit for preventing the excessive buildup of ice slab thickness on a refrigerated inclined plate over which water is circulated by an electric motor driven recirculating pump during a refrigeration phase and wherein an electrical defrost means is associated with the refrigerated plate to remove a slab of ice therefrom, the released slab of ice being received by an energized electrical grid for cutting the slab into a plurality of cubes of ice comprising: Circuit means defining an energization circuit across a power source for the pump motor including first and second switch means, first and second electrically energizable solenoid means for positioning said first and second switch means to control the energization of said pump motor circuit, second circuit means for energizing the defrosting means including a back contact selectively engageable by said first switch means when operated to deenergize the pump motor, means for selectively controlling energization of said first solenoid means including a first transistor having a base, electrode and emitter electrodes connected in circuit with said first solenoid means, means for directing a biasing current to the base of said first transistor including a normally closed third switch actuated by said first solenoid means and further including a first ice thickness sensing mercury thermostat, means including a tilt switch responsive to movement of a slab of ice onto the cutting grid having one terminal thereof connected to the base of said first transistor and the opposite terminal thereof connected to the power source and operative when a slab of ice has been released onto the grid to terminate the base biasing signal to said first transistor to interrupt the energization circuit for said first solenoid, and means for preventing an excessive buildup of ice on the refrigerated slab including a second ice thickness sensor mercury thermostat positioned to detect an excessive buildup of ice slab thickness, a second transistor having base, collector and emitter electrodes, said second solenoid means being connected across the collector emitter electrodes of said second transistor for enErgization across the power source, biasing means including said second ice thickness sensor mercury thermostat for directing a signal to the base of said second transistor when an excessive ice slab thickness is detected to condition said second transistor to energize said second solenoid means thereby to condition said second switch means to terminate energization of the water pump motor when said slab switch is maintained closed following a previous defrost cycle.

Claim 6

A control circuit for preventing the excessive buildup of ice slab thickness on a refrigerated inclined plate over which water is circulated by an electric motor driven recirculating pump during a refrigeration phase and wherein an electrical defrost means is associated with the refrigerated plate to remove a slab of ice therefrom, the released slab of ice being received by an energized electrical grid for cutting the slab into a plurality of cubes of ice comprising: Circuit means defining an energization circuit across a power source for the pump motor including first and second switch means, first and second electrically energizable solenoid means for positioning said first and second switch means to control the energization of said pump motor circuit, second circuit means for energizing the defrosting means including a back contact selectively engageable by said first switch means when operated to deenergize the pump motor, means for selectively controlling energization of said first solenoid means including a first transistor having a base, electrode and emitter electrodes connected in circuit with said first solenoid means, means for directing a biasing current to the base of said first transistor including a normally closed third switch actuated by said first solenoid means and further including a first ice thickness sensing mercury thermostat, means including a tilt switch responsive to movement of a slab of ice onto the cutting grid having one terminal thereof connected to the base of said first transistor and the opposite terminal thereof connected to the power source and operative when a slab of ice has been released onto the grid to terminate the base biasing signal to said first transistor to interrupt the energization circuit for said first solenoid, and means for preventing an excessive buildup of ice on the refrigerated slab including a second ice thickness sensor mercury thermostat positioned to detect an excessive buildup of ice slab thickness, a second transistor having base, collector and emitter electrodes, said second solenoid means being connected across the collector emitter electrodes of said second transistor for enErgization across the power source, biasing means including said second ice thickness sensor mercury thermostat for directing a signal to the base of said second transistor when an excessive ice slab thickness is detected to condition said second transistor to energize said second solenoid means thereby to condition said second switch means to terminate energization of the water pump motor when said slab switch is maintained closed following a previous defrost cycle.

Claim 7

A control circuit for preventing excessive buildup of thickness in a slab of ice on a refrigerated plate in an automatic ice maker of a type including a refrigerated plate having water recirculated thereacross by an electric motor driven pump to form an ice slab thereon and with an ice harvest cycle being initiated when a predetermined ice slab thickness occurs and including means for defrosting the refrigerated plate to cause the formed ice slab to slide onto an ice cube cutting grid, the control circuit comprising in combination: a first ice thickness control thermostat switch, a grid switch actuatable when a slab of ice slides from the refrigerated plate onto the cutting grid, a first npn transistor having a base, an emitter, and a collector, a direct current power source having first and second terminals, one of said terminals being connected to said grid switch and said first thermostat switch, means including a biasing resistor for connecting the other of said power source terminals to the base of said first transistor, normally closed first switch means connecting said transistor base through said first thermostat switch to the other power terminal, second switch means having a normally closed contact for energizing means for circulating water across the refrigerated plate and a normally open contact, means including said normally opened contact to define an energization circuit for operating the defrost means for the refrigerated plate, said biasing resistor being selected so that when a predetermined temperature is sensed by siad first ice thickness control thermostat switch a current flow will be directed through the base emitter circuit of said first transistor to cause it to be conductive between the collector-emitter circuit thereof, first solenoid means connected in circuit with the collector-emitter circuit of said first transistor and energizable when said first transistor is triggered conductive to condition said first switch means to open and to condition said second switch means to close the normally open contact thereof thereby to terminate water circulation and to initiate defrost and an ice slab harvest cycle, a normally open ice slab grid switch connected between the base of said first transistor and one of the power source terminals and operative when the slab of ice has been released to reverse bias the base emitter circuit of said first transistor to terminate energization of said first solenoid means thereby to terminate defrost of the refrigerated plate and to reinstitute recirculation of water across the refrigerated plate, and means for preventing excessive build-up of ice when the normally open slab sensing grid switch is closed by the presence of an uncut ice slab on the grid including a second ice thickness control thermostat switch located with respect to the refrigerated plate to detect an excessive buildup in the thickness of an ice slab thereon, a second npn transistor including a base, collector and emitter, circuit means for connecting the base of said second transistor across the power source terminals including a biasing solenoid means, means for connecting said second solenoid means across the power terminals including the collector-emitter of said second transistor, a normally closed switch means in the energization circuit for the water pump circuit operated by said second solenoid means when the second transistor is conductive between the collector and emitter electrodes thereof, said second thermostat switch being responsive to an excessive buildup of ice thickness as produced when the grid switch is maintained closed during a refrigerated, recirculating water phase of operation to produce a biasing signal on the base of said second transistor to trigger said second transistor conductive thereby to energize said second solenoid means and condition said second switch means to deenergize the water recirculation pump circuit thereby to terminate further buildup of ice thickness on the slab.

Claim 8

A control circuit for preventing excessive buildup of thickness in a slab of ice on a refrigerated plate in an automatic ice maker of a type including a refrigerated plate having water recirculated thereacross by an electric motor driven pump to form an ice slab thereon and with an ice harvest cycle being initiated when a predetermined ice slab thickness occurs and including means for defrosting the refrigerated plate to cause the formed ice slab to slide onto an ice cube cutting grid, the control circuit comprising in combination: a first ice thickness control thermostat switch, a grid switch actuatable when a slab of ice slides from the refrigerated plate onto the cutting grid, a first npn transistor having a base, an emitter, and a collector, a direct current power source having first and second terminals, one of said terminals being connected to said grid switch and said first thermostat switch, means including a biasing resistor for connecting the other of said power source terminals to the base of said first transistor, normally closed first switch means connecting said transistor base through said first thermostat switch to the other power terminal, second switch means having a normally closed contact for energizing means for circulating water across the refrigerated plate and a normally open contact, means including said normally opened contact to define an energization circuit for operating the defrost means for the refrigerated plate, said biasing resistor being selected so that when a predetermined temperature is sensed by siad first ice thickness control thermostat switch a current flow will be directed through the base emitter circuit of said first transistor to cause it to be conductive between the collector-emitter circuit thereof, first solenoid means connected in circuit with the collector-emitter circuit of said first transistor and energizable when said first transistor is triggered conductive to condition said first switch means to open and to condition said second switch means to close the normally open contact thereof thereby to terminate water circulation and to initiate defrost and an ice slab harvest cycle, a normally open ice slab grid switch connected between the base of said first transistor and one of the power source terminals and operative when the slab of ice has been released to reverse bias the base emitter circuit of said first transistor to terminate energization of said first solenoid means thereby to terminate defrost of the refrigerated plate and to reinstitute recirculation of water across the refrigerated plate, and means for preventing excessive build-up of ice when the normally open slab sensing grid switch is closed by the presence of an uncut ice slab on the grid including a second ice thickness control thermostat switch located with respect to the refrigerated plate to detect an excessive buildup in the thickness of an ice slab thereon, a second npn transistor including a base, collector and emitter, circuit means for connecting the base of said second transistor across the power source terminals including a biasing solenoid means, means for connecting said second solenoid means across the power terminals including the collector-emitter of said second transistor, a normally closed switch means in the energization circuit for the water pump circuit operated by said second solenoid means when the second transistor is conductive between the collector and emitter electrodes thereof, said second thermostat switch being responsive to an excessive buildup of ice thickness as produced when the grid switch is maintained closed during a refrigerated, recirculating water phase of operation to produce a biasing signal on the base of said second transistor to trigger said second transistor conductive thereby to energize said second solenoid means and condition said second switch means to deenergize the water recirculation pump circuit thereby to terminate further buildup of ice thickness on the slab.